The catalytic deamination of alkyl diamino benzenes to alkyl amino benzenes, particularly the catalytic deamination of toluene diamine to toluidine has been achieved by effecting the hydrogenation in the presence of a base promoted cobalt oxide catalyst. In this type of process ring hydrogenation has been a significant problem particularly where the catalyst consists of a cobalt oxide-calcium oxide-sodium carbonate material.
U.S. Pat. No. 3,532,754 discloses an improvement in the catalytic deamination process of diamino benzenes and uses a supported cobalt catalyst to effect the deamination. A cobalt hydrogenation catalyst supported on kieselguhr, alumina, silica, carbon or various other supports, and preferably promoted with sodium carbonate or an alkaline earth oxide, is used.
It is also known that the hydrogenolysis of o-toluidine to toluene can be affected over a nickel catalyst. However, the use of a nickel catalyst generally results in substantial ring hydrogenation.